A technique of improving bias of lightness such as brightness or luminance in a technique of correcting images captured by commercial digital still cameras and wide dynamic range camera (having expressiveness equal to or more than 8 bits of R, G and B colors) is gaining attention. A processing target image is mainly corrected using a single brightness characteristic to improve bias of, for example, brightness, and, for a function of correcting the brightness characteristic includes, for example, a gamma correction function, a logarithmic function or a function defined using statistical processing such as histogram averaging is used.
Further, following a spread of broadband internet connection such as optical fibers and an increase in the resolution of movies and the like such as high-definition television broadcast, devices such as digital still cameras and digital video cameras provide higher image quality such as several mega pixels to giga pixels, and are required to provide a higher speed of image processing and higher accuracy.
Hence, for example, Patent Document 1 discloses an image processing device which obtains a gradation compression image to adequately emphasize a contrast of an image at a higher speed. Further, as to higher accuracy, Patent Document 2 discloses an image processing device which sets a local area, calculates a local histogram related to lightness in the local area, accumulates a local histogram and calculates a local cumulative histogram, determines each of monotonically increasing functions corresponding to a cumulative numerical value in each class of the local cumulative histogram, determines each of weighting functions for each monotonically increasing function, generates a conversion function of lightness of a pixel from each monotonically increasing function weighted by the weighting function and converts lightness of the pixel.